It’s always fun having debates about city densities and public transport. A post by Jarrett Walker at Humantransit.org makes an excellent contribution to the debate – as we seek to answer the age old question of “does density matter when it comes to the viability of public transport?” As I noted in a blog post a while back, there’s an ugly myth that perpetuates thinking in Auckland, the myth being that we are one of the lowest density cities in the world, and therefore public transport won’t work.
In that particular post, I had a good dig through a very detailed set of statistics on city sizes, both in terms of area and population (and therefore obviously in terms of density). Some of the results were probably quite surprising for some. Here’s the list of selected cities by density: While obviously Auckland’s density is well below many of the large developing world cities like Mumbia and Dhaka, somewhat surprisingly our density is higher than Sydney, Vancouver, Melbourne, Perth, Brisbane and even that of greater New York. Yet all of these cities have public transport systems that function far better than Auckland’s and are far more popular – even Brisbane with its population density of less than half of Auckland’s.
Melbourne based transport academic Paul Mees used this data in his excellent book Transport for Suburbia to argue that “density is not destiny”. I wrote a blog post on that matter earlier this year outlining Mees’s argument that, while population density might have some effect on public transport use at the extreme ends of the scale (in that it’s utterly essential for somewhere like Hong Kong to function, and damn near impossible to operate effectively somewhere like Atlanta), in the middle where most cities are other factors – such as the simple quality of the public transport system – are likely to have far greater impact on whether or not people use the system than density will.
While one could be negative about such a finding, wondering whether it removes one of the big arguments for trying to contain sprawl, there’s also the big potentially positive point-of-view that “we can still have a great public transport system, even when our city isn’t enormously dense“. This is basically why Mees has written Transport for Suburbia, to show cities like Auckland that we shouldn’t wait around for another 50 years, hoping that our city will end up looking like a dense European city, before finally getting around to properly improving our public transport system. I fully agree with this and it annoys the heck out of me when people like John Banks continue to go on about Auckland being the “second most spread out city in the world” (presumably Los Angeles in the first, even though the statistics actually show LA is the densest city in the USA) to help justify why we need to complete the road network before getting around to focusing on the public transport system.
However, there’s also something in the “density is not destiny” argument that doesn’t quite feel right. Visiting one of the densest places on earth, Manhattan, and seeing the tremendous number of public transport users such an urban environment generates (due to lack of space for parking, building roads and so forth) does make it difficult to believe that the relationship between population density and public transport use isn’t significant. But if that’s the case, why do we get such weird numbers like this: Looking at those numbers, one would just about have to conclude that there seems to be absolutely zilch relationship between density and transit mode share for work trips. Yet that seems illogical – so what’s going on here?
This is where Jarrett’s post comes in to make some excellent points – including asking some very necessary questions.
But emotions often hide inside things that look like facts, and density “facts” are a great example. In transit arguments, people say things like “the net density of Toronto is ###/hectare,” because this sounds like a fact and therefore conveys some authority to their argument. In reality, though, there are several possible meanings of “density” in that sentence, as well as several possible definitions of “net” and ”Toronto.” Briefly:
- “Density” in an urban planning context is always some kind of quantified human presence divided by some kind of land area, but it can be residential density (residents or homes per acre) or it can be total development density — including homes, businesses, schools etc – or it can be an economic density such as the number of jobs in an area.
- “Net,” as opposed to “gross,” means that the human presence is being divided by a smaller unit of area instead of a larger one. In calculating the area, for example, you might take out undevelopable land, and bodies of water, and the land taken up by streets and highways — or you might not. There are arguments for or against excluding each of these things from “net density,” and an opinion about each of them is hiding inside the word “net.”
- “Toronto,” of course, can be the City of Toronto, or the Toronto Transit Commission area, or the whole urban mass of greater Toronto. These obviously have utterly different average densities.
So the statement “the net density of Toronto is ###/hectare” is really as subjective as the statement “I think that cities should have more open space, narrower streets, and should have single governments covering the entire urban area.” Because each of those opinions can affect how you choose to define “net,” “density,” and “Toronto,” which in turn determines the number that you declare, with cold factual authority, to be the net density of Toronto.
So really how do we know whether we’re comparing apples with apples? This is a point that Mees makes quite strongly in his book though, that many of the past analysis of population density have been flawed through inconsistent measurements. He has certainly tried very hard to make sure his statistics don’t fall into the same trap, but it just goes to show something seemingly as simple as calculating the population density of the a city is actually very complex indeed. A corollary to this of course is the question of “how much does the density of outer outer New York really matter when assessing the city as a whole’s suitability for public transport? Isn’t the fact that it has hugely dense inner suburbs vastly more important?
This leads on to the question of whether the reason we’re getting such weird results is actually because we’re using the completely wrong measuring stick – in the form of average density. This is what Jarrett argues:
To me, Mees’s table proves that average density over a whole urban area is the wrong kind of density for understanding transit. The impression you probably have of the densities of these cities is actually closer to the kind of density that matters.
Transit reacts mainly with the density right around its stations. It is in the nature of transit to serve an area very unevenly, providing a concentrated value around its stops and stations and less value elsewhere. So what matters for transit is the density right where the transit is, not the aggregate density of the whole urban area.
Of course, what matters even more precisely is how much stuff is within walking distance of a station, so it’s not just density (the amount of stuff in a fixed radius) but the completeness of the pedestrian network. A poor connected pedestrian network can ensure that much of the stuff that’s within a 400m radius is not in a 400m walk. Consider Las Vegas, which Mees finds to be denser than highrise Vancouver. The Las Vegas economy is based on hospitality and entertainment, labor-intensive industries with low average wages. So the city needs a lot of housing suited for lower incomes. The Las Vegas way is to build utterly car-dependent apartment buildings on a vast scale, achieving all of the disadvantages of density with none of its benefits.
I completely agree. What matters is not what the density of a city is, but it’s how that density is structured. Do we have higher areas of density clumped around train stations – like you see in Canadian cities such as Toronto and Vancouver – or do we see the uniform densities of Auckland and Los Angeles? Furthermore, how conducive to public transport are our street patterns? What is the environment like for someone wanting to walk to public transport from their house? It is highly arguable that all of these issues matter far more to the success or failure of public transport in a city, than average density does.
So, returning to Mees’s question – is density destiny? I would certainly argue that average density has nothing to do with our public transport destiny: just compare New York and Los Angeles for your answer there. However, urban densities around public transport – particularly around rail – will determine the success or failure, the destiny, of that public transport system. Park and rides, feeder buses and so forth can all help in making public transport work better in low density areas, but ultimately if you want a situation where people don’t feel as though they have to own a car to live a meaningful life – I really do think you’re going to need some density.